Restore Buffer::file field and workspace::Item trait

zed/src/editor/display_map/mod.rs

@@ -324,7 +324,7 @@ mod tests {
     fn test_chars_at() {
         App::test((), |app| {
             let text = sample_text(6, 6);
-            let buffer = app.add_model(|_| Buffer::new(0, text));
+            let buffer = app.add_model(|ctx| Buffer::new(0, text, ctx));
             let map = app.add_model(|ctx| DisplayMap::new(buffer.clone(), 4, ctx));
             buffer
                 .update(app, |buffer, ctx| {
@@ -391,7 +391,7 @@ mod tests {
     #[test]
     fn test_max_point() {
         App::test((), |app| {
-            let buffer = app.add_model(|_| Buffer::new(0, "aaa\n\t\tbbb"));
+            let buffer = app.add_model(|ctx| Buffer::new(0, "aaa\n\t\tbbb", ctx));
             let map = app.add_model(|ctx| DisplayMap::new(buffer.clone(), 4, ctx));
             assert_eq!(
                 map.read(app).max_point(app.as_ref()),